Spinocerebellar ataxia-1 (SCA1) is a devastating neurological disorder, resulting from CAG repeat expansion in the ataxin-1 gene. The polyglutamine expanded mutant ataxin-1 primarily targets Purkinje cells (PCs) of the cerebellum. The exact mechanism of PC degeneration in SCA1 is poorly understood, but it is known that the earliest morphologic change seen in SCA1 PCs is the development of cytoplasmic vacuoles that contain Bergmann glial (BG) proteins, especially S100B. These vacuoles are toxic and alter PC morphology, and may be forming in response to a stress signal of PCs. Furthermore, S100B released by BG or from the vacuoles may modulate Akt phosphorylation of mutant ataxin-1. Akt is known to stabilize mutant ataxin-1 to aggregate in the nucleus of PCs. The objective of the proposed study is to target SCA1 PCs with therapeutic peptide (TP) that will influence ataxin-1 aggregation and toxicity. Though TPs are designed to inhibit specific molecular interactions, their efficacy in vivo is limited by poor pharmacokinetic parameters. To improve their pharmacokinetics and bio-distribution, TP will be fused to a thermally responsive polypeptide-based carrier. This polypeptide can be targeted to the cerebellum of Tg mice by applying local hyperthermia. The amino acid sequence of the thermally responsive polypeptide is based on elastin-like polypeptide (ELP) biopolymers, which are soluble in aqueous solution below physiological temperature, but aggregate when the temperature is raised above 39oC. A cell-penetrating peptide (CPP) is conjugated to the ELP to enhance delivery of the polypeptide across the blood brain barrier (BBB) and to facilitate cell entry. To the CPP-ELP, therapeutic peptide TRTK-12, which interacts with S100B will be conjugated. This TP will be administered intranasally (IN) or intraperitoneally (IP) and, by applying local hyperthermia, it will be demonstrated that these genetically engineered polypeptides can be targeted to a diseased site and improve motor coordination and cerebellar pathology in a SCA1 mouse model. This project will address the following specific aims: Specific Aim 1: Determine feasibility of delivering Bac-ELP or SynB1-ELP IN or IP to the cerebellum. The plasma kinetics and the in vivo distribution of radio-labeled Bac/SynB1-ELP will be measured in the cerebellum, other brain regions and tissues in a SCA1 mouse with and without hyperthermia. Specific Aim 2: Evaluate the therapeutic efficacy TRTK-12 attached to the optimal CPP-ELP as determined in Specific Aim 1. It is anticipated that TP treatment will result in improved motor coordination and PC pathology and will provide preclinical support for the therapeutic potential of this novel technology. Though the SCA1 mouse will be used as a model in the proposed work, this approach could also be applied to thermal targeting of ELP-fused TPs to many other CNS disorders. Therefore, successful completion of the proposed research may have a significant impact, by not only propelling this technology into clinical trials, but also providing a powerful tool to treat and manage other CNS diseases. PUBLIC HEALTH RELEVANCE: Spinocerebellar ataxia-1 (SCA1) is a devastating neurological disease resulting from CAG repeat expansion in the ataxin-1 gene, leading to polyglutamine expansion at the protein level, and degeneration of Purkinje cells as well as some other cell types in the brainstem. Currently, there is no specific treatment to delay or halt the progression of SCA1. We plan to use a very unique strategy of thermally targeted delivery of candidate therapeutic peptides to the cerebellum via intranasal or intravenous routes with the goal of developing useful new strategies for treating SCA1 and other ataxias.